Geophysics with earth science I am a communications engineering student. I am interested in doing a project on geophysics. The concept is for a hole-digging robot with a camera and sensors and wireless transmitter that is made of high mp alloys. It is intended to make a hole down to 3000 km and perform a sample-return for any interesting things that could be found at that depth. This could help scientists learn more about the interior of Earth. Is this something that could be done?
 A: The radius of the Earth is about 6,400km so you are talking about digging a hole almost halfway to the centre of the Earth. This is far beyond our current technology.
I wonder if you meant 3,000m rather than 3,000km. The deepest borehole ever dug is the Kola borehole, which got down to 12km so 3km is certainly possible.
A: At 3000km, even if the structure of the robot survived, all of the sensitive equipment would certainly melt. Furthermore, communication with the robot would be impossible as molten rock would quickly fill in the hole behind the robot and re-solidify. This means there would effectively be (at the very least) several hundred kilometres of solid mantle between you and the robot. No radio signal could penetrate that.
3000 km is in the outer core. A region comprised mostly of liquid iron and nickel with a minimum temperature around 4300K and a background magnetic field 50 times that at the surface. Not only that, but this robot would be swept along by the turbulent eddies within the outer core and subjected to the extreme pressures in that zone (over 1.4 million atmospheres). If, somehow, it isn't completely melted or crushed, the robot will not be able to communicate or return.
So in short, no, this could not be done.
